The present invention relates to medical devices, and specifically to surgical instruments with blades or “trephines.” A trephine is a surgical instrument with a cylindrical blade that is commonly used in medical procedures to create a circular incision around an area of interest. A trephine usually includes a hollow metal cylinder with one end of the cylinder having a sharp incising edge. Trephines are also used during ophthalmic surgery in order to correct a corneal defect of a living patient. Radial keratotomy, astigmatic keratotomy, penetrating keratoplasty, and lamellar keratoplasty are common surgical procedures that are known to utilize a trephine. Trephines are also used in corneal transplantation and in cadaveric surgical cornea recovery procedures.
Radial and astigmatic keratotomies are refractive surgeries where the surgeon attempts to correct a patient's corneal curvature. In this procedure, the surgeon first determines the optical zone or specific portion of the cornea which is to remain uncut. Determining and marking this portion of the cornea is typically accomplished by using a trephine and/or specific dyes. When the trephine incising edge is pressed onto the corneal epithelial surface of a patient, it produces a visible imprint on the cornea that encircles and marks the cornea optical zone. The trephine edge can also be coated with marking ink which leaves an ink imprint on the cornea surface when pressed against the cornea epithelial tissue. In radial keratotomy and astigmatic keratotomy a blade is used to create precise incisions on the surface of the cornea outside the marked optical zone. Through specific incisions on the corneal tissue of the patient, the surgeon can modify and correct the corneal curvature.
In a corneal transplantation procedure, a surgeon replaces all or part of a patient's diseased or damaged cornea with donated cadaveric corneal tissue. Penetrating keratoplasty is the procedure in which all layers of the living patient's cornea are replaced and lamellar keratoplasty is the procedure in which a portion or layer of a living patient's cornea is replaced. In keratoplasty procedures the center of the diseased or damaged portion of the cornea is marked through the use of dyes or by pressing or incising the cornea. The surgeon places a trephine over the center of the marked cornea and creates a circular incision on the corneal tissue. The diameter of the trephine is typically under 10.00 mm and will vary depending on the extent of the damaged or diseased area of the cornea. The surgeon removes the diseased or damaged portion of corneal tissue and replaces it with healthy donor cornea tissue by sewing it in place with sutures to the patient's remaining corneal tissue.
In refractive eye surgery and corneal transplantation surgery, trained physicians utilize a combination of resources including microscopes, vacuum suction, specific dyes, blades, and smaller trephine diameter sizes in order to mark areas of a living patient's corneal tissue and stabilize their devices. Several types of devices have been proposed to hold a variety of different trephine diameters. For example, U.S. Pat. Nos. 4,319,575 and 4,429,696 are both multi-part devices that provide different diameter trephine blades by modifying the trephine blades to have an interior shoulder, outward radial arm projections and/or screw threads. Other patents have attempted to describe ways to align their device over a specific area of the eye to assist in refractive surgery and keratoplasty procedures. U.S. Pat. No. 6,632,232 and CN patent 102846429A utilize a single reticle or crosshair design to assist with alignment. While a single crosshair still requires the user to estimate the center of the patient's eye, some devices attempt to minimize this problem by utilizing a combination of microscopes, dyes, and/or physically marking the cornea prior or during the placement of the device to assist with the alignment. Other devices include U.S. Pat. No. 4,875,767 which proposes a device with sliding opaque disks with pinholes that obscures other portions of the eye while allowing the user to visualize the patient's fovea and physically mark the center of the cornea epithelium. U.S. Pat. No. 5,578,049 is a metal device that discloses two levels of overlapping indicator pointers used in conjunction with a microscope to estimate the center of the pupil. Although the overlapping indicator pointers may be useful at a number of distances, they may prove problematic the closer the user's vision approaches the top pointer, as it would obscure the bottom pointer.
Cadaveric surgical cornea recoveries are typically performed by a tissue surgical recovery technician employed by a tissue bank. Tissue banks do not have the same resources that are available to hospitals and tissue recovery technicians are minimally trained compared to the rigorous instruction that physicians receive. The cadaveric surgical cornea recovery takes place in a variety of environments. While the optimal environment is an operating room, cadaveric surgical cornea recoveries also take place in morgue anterooms, pathology suites, and funeral homes. In a cadaveric surgical cornea recovery, a tissue recovery technician typically uses a larger diameter 18.00 mm sterile metal trephine. The larger diameter trephine is utilized to avoid contact with the corneal tissue and to create a circular incision on the sclera of the donor's eye. As a sterile procedure, the technician applies pressure to the speculum with one hand in order to stabilize the donor's eye and maintain eyelid separation. The technician utilizes their free hand to manually place the trephine over the center of the eye or pupil and manually rotates the trephine to create a circular incision on the sclera of the eye. The goal is to avoid any contact with the corneal tissue and to create a circular incision around the center of the eye, resulting in a specific uniform scleral width or scleral rim size. The scleral rim size is a determinant if the corneal tissue can be later processed for transplantation. If the scleral rim size is too small or too large in diameter, the tissue cannot be processed and utilized in keratoplasty surgeries for living patients. Additionally, if the corneal tissue is contacted during the procedure this may result in corneal epithelial damage that may render the tissue unusable for transplant. Placement of the larger diameter trephine on the sclera of the donor cadaver eye is estimated by the tissue recovery technician, resulting in inaccuracy that may render the surgically recovered cadaveric corneal tissue non-viable for transplant.
It would be desirable to have a device and a method that provides a reproducible and accurate alignment of a trephine over an eye in order to extract intact and unmarked corneal tissue with uniform scleral width of specific dimensions.